BELBEK AIR BASE, Ukraine, March 4 (Reuters) - Perched on a cliff high above the Black Sea, Ukraine's Belbek military air base and its MiG-29 fighter jets fell into the hands of forces loyal to Russian President Vladimir Putin late last week.

On Tuesday, the Ukrainian air force and the men who until recently used to fly its war planes, tried and failed to get it back.

The standoff was one of the most dramatic since pro-Russian forces began to try to seize Ukraine's military assets on the Crimean peninsula, where Russia's Black Sea Fleet is based.

Colonel Yuli Mamchur, commander of Ukraine's 204th tactical aviation brigade, led hundreds of his men up the long winding road from their barracks to the cliff top airstrip in a column early on Tuesday.

Carrying the blue and yellow Ukrainian flag and a red Soviet-era banner, his men - who said they thought they were facing off against more than 300 Russian soldiers - were unarmed.

As they marched past rusting radar dishes and the desolate carcass of a Soviet helicopter gunship, they sang the Ukrainian national anthem.

"Keep walking. We rule here! America is with us!" bellowed a voice, as the men, many of whom wore traditional fur hats, marched towards a spot where they knew the Russians were blocking the airfield.

Their demand: to be allowed to guard their own base along with Moscow's men and to carry out their usual duties.

Ahead of them, on a narrow tarmac road, loomed a squat 'Tiger' armoured car - Russia's answer to the U.S. Humvee.

Three men clutching Kalashnikov assault rifles stood in front of it. On the left, snipers had taken up position behind a ridge. Guns were also trained on the airmen from the right.

As they strode forward, the three gunmen shouted at them to stop. The Ukrainians marched on.

One of the gunmen then raised his Kalashnikov rifle in the air and fired off a staccato volley of warning shots, the first of three such volleys.

The crackle of gunfire prompted some to duck, but the Ukrainians carried on before stopping just short of the gunmen.

Mamchur, the Ukrainian colonel, then stepped forward and spoke to one of the armed men, the first of several exchanges.

The standoff dragged on. In one surreal moment, some of the Ukrainians even began to play football on the grass next to the road to pass the time as the gunmen looked on.

The incident ended quietly. Hours later, and after much wrangling and many phone calls, Mamchur told reporters he had decided to take his men back down the hill to wait to hear from the Russians whether they would hand him back his base.

"The aerodrome is completely under the Russians' control," he said. "I've told them I'll take my people back down and wait for them to call me."

He did win one concession though - for around 10 of his men to remain to jointly guard the military facility.

Down below at the barracks, the wives of some of the airmen had stayed up all night keeping a vigil at its gates to try to protect their husbands.

When asked how long he thought the standoff could go on, Colonel Mamchur replied: "God knows". (Editing by Will Waterman)